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Abstract
Sheep in which the efferent duct of the caudal mediastinal lymph node was cannulated were exposed to 5 ppm NO 2 , 1.5 h/d for 10 or 11 d. Immune responses were assessed by measuring the daily output of hemolytic plaque‐forming cells (PFC) in pulmonary lymph, following intrabronchial immunization with horse red blood cells (HRBC) and phytohemagglutinin‐ (PHA) induced transformation of blood and pulmonary lymph lymphocytes. Sheep immunized 2 d after termination of NO 2 exposure had reduced outputs of PFC as compared to those seen in sheep challenged 4 d after NO 2 exposure. Animals immunized 4 d after NO 2 exposure had outputs similar to those of air control sheep. A reduction of 38–87% in the transformation index of both blood and pulmonary lymph lymphocytes was observed in sheep exposed to NO 2 . These results suggest that intermittent, short‐term exposure to 5 ppm NO 2 may temporarily alter pulmonary immune responsiveness.
